Can HF Radar detect Tsunamis ?

The 11th March 2011 Sendai Tsunami could be observed at the coast of Cile
close to Conception 22 hours after generation.
First results have been presented on the
ROS 2011 workshop.

After the tsunami disaster at 26th December 2004 causing more than 260,000
lifes lost, the possibilities of HF radar
to detect tsunami waves have been investigated. In contrast to wind-driven
ocean surface waves, a tsunami's energy is distributed all along the water
column from the surface to the bottom of the ocean. In wave theory, tsunamis
have to be considered as shallow water waves, thus the tsunami's speed can be
calculated by
v = sqrt(g h)

In the deep ocean, where the speed of a tsunami is in the order of 700 km/h
at a waveheight of less than one meter, there is most probably no signature
connected to the tsunami which can be seen by HF radar. However, when the
tsunami travels into shallow water, e.g. at the shelf edge, the tsunami slows
down in speed and gets transformed to a shorter wavelength. This process is
connected to a strong ocean current signature along the tsunami front. As the
bottom topography along the path of the tsunami plays a significant role if
one wants to describe the tsunami's waheheight and the connected current
pattern as a function of time, a numerical model simulation has been performed
for the area of

using the initial conditions given by the strength and location of the
earthquake of 26 December 2004.

The model results presented above show current fields
with speeds up to 2 m/s which provide some evidence that such features can
be most probably be detected and tracked by HF-radar, presumed that the radar
technology allows for sufficient short integration times (roughly 4-5 minutes),
as the tsunami 'signature' is very quickly passing through the radar ranges.
This should be possible with WERA. Further investigations will be conducted in the
near future.